1. Field of the Invention
The present invention relates to transitory alarm systems.
2. Description of the Prior Art
The control of industrial plants includes the alarm surveillance of the states of the process variables associated with the plant, such as magnitude and change in magnitude of the pressures and temperatures. It is known in the art to perform such surveillance by use of electronic alarm systems monitoring the states of such variables. Such electronic alarm systems are usually contained in several large panels, each panel including numerous alarm indicators. Typically, there is an alarm indicator for each state monitored. The alarm indicator is usually a combination of a translucent nameplate and a lamp located behind the nameplate. The blinking of an alarm indicator lamp by an annunciator circuit accompanied by an audible signal is normally used to indicate the presence of a previously undetected abnormally deviant value of the state to a human operator. The operator, after identifying the variable from the blinking light, normally acknowledges the signal by actuating a portion of the annunciator circuit that silences the audible signal and inhibits further blinking of the lamp. The operator thereafter takes whatever action, if any, is necessary to remedy any problem in the industrial plant that may be causing the abnormally deviant value. The lamp is usually maintained in a steady burning condition by the circuit until the state has again reached a value within the permissible boundaries for the variable, at which time the lamp is turned off by the circuit. The effective use of such an alarm system mandates the ability to quickly detect any faulty lamps and replace them. The usual practice in the prior art is to provide each panel with a special test button that turns on all lamps. A faulty lamp may then be detected by ones that are not on.
However, none of the prior art alarm systems teach the use of additional electronic circuitry to enable the operator to determine which panels include indications of unacknowledged alarms. This would be especially useful when an audible signal is sounded indicating an alarm has occurred, and no light associated with a variable is blinking on any of the panels. Such a condition in the prior art systems requires all panels to be tested until the faulty lamp or lamps are located. It would also be useful when one light is blinking on one panel, but another light which should be blinking on another panel is burned out.
The control of industrial plants also includes the manipulation of valves and motors. The current state of such valves and motors is usually indicated on a graphic or semigraphic display by the use of lamps mounted behind a graphical depiction of the controlled plant. None of the prior art, however, utilizes a momentary flash of a light or audible signal or other indicator responsive to a change in any state of the valves and motors to call the attention of the operator to such a change.